Doubly Linked List : Insert at Front

Doubly Linked List : Insert at  Front

#include<stdio.h>

#include<stdlib.h>

struct node

{

        int data;

        struct node *llink;

        struct node *rlink;

};

typedef struct node* NODE;

NODE getnode();

NODE insert_at_front(NODE first, int item);

void display(NODE first);

NODE getnode()

{

        NODE x;

        x = (NODE) malloc(sizeof(struct node));

        x->llink=NULL;

        x->rlink=NULL;

        return x;

}

NODE insert_at_front(NODE first, int item)

{

        int val;

        NODE temp;

        temp = getnode();

        temp->data = item;

        if(first == NULL)                       /*Case 1: List is empty*/

        {

                   return temp;

        }

        temp->rlink = first;                   /*Case 2: List not empty. Insert temp node at front of list.*/

        first->llink = temp;

        return temp;

}

void display(NODE first)

{

            NODE cur;

            cur = first;

            printf("\nContents are:");

            if(cur == NULL)

                        printf("\nDoubly Linked List is empty. Nothing to display.");

            else

            {

                        while(cur!=NULL)

                        {

                                    printf("%d  ", cur->data);

                                    cur = cur->rlink;

                        }

            }

}

void main()

{

            int ch, item;

            NODE first = NULL;

            while(1)

            {

                        printf("\n\n~~MENU~~");

                        printf("\n1.Insert at front");

                        printf("\n2.Display");

                        printf("\n3.exit");

                        printf("\nEnter your choice: ");

                        scanf("%d",&ch);

                        switch(ch)

                        {

                                    case 1:            printf("\nEnter the value: ");

                                                            scanf("%d", &item);

                                                            first = insert_at_front(first, item);

                                                            break;

                                    case 2:             display(first);

                                                            break;

                                    case 3:           exit(0);

                        }

            }

}

Output:

~~MENU~~

1.Insert at front

2.Display

3.exit

Enter your choice: 1

Enter the value: 11

~~MENU~~

1.Insert at front

2.Display

3.exit

Enter your choice: 1

Enter the value: 12

~~MENU~~

1.Insert at front

2.Display

3.exit

Enter your choice: 2

Contents are: 12        11

~~MENU~~

1.Insert at front

2.Display

3.exit

Enter your choice: 3